JPS5941620B2 - Loopback method of dual loop transmission system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION 5 The present invention relates to measures against failures in loop transmission systems.

Figure 1 shows the general configuration of a dual loop transmission system. In the figure, 1 is used to generate the synchronization necessary for loop transmission, to monitor system failures, and to control recovery from failures. The monitoring station CST) 2 is a station T51 that enables communication between scattered terminals.
~TS3, 3 and 4 are transmission lines that transmit signals in opposite directions, 5 is a stage for connecting various terminals to station 2), 6 to 9 are printers, operation consoles,
These are display devices and calculators.

FIG. 2 shows the general configuration of the station when the dual loop transmission system is completely normal.

In the figure, 21a and 21b are transmission lines '3 and 4, respectively.
The receivers 22a and 22b for each transmission line 3
, 4, and 24 is a transmission/reception control circuit that performs input/output with the station bus 5 and relays transmission line signals. If a failure occurs in transmission line 3, 24
is inserted between 21b and 22b, and the output of 21a and 22a
Although it is possible to switch directly to the input of , this switching function is omitted in FIG. 2. FIG. 3 shows the concept of loop back when both double system loops are broken at the same point.

In the figure, transmission lines 3 and 4 are connected between stations ST2 and ST3.
are both disconnected, and loopback is performed at stations ST2 and ST3 toward monitoring station CST, respectively, and a new loop is constructed using both transmission lines 3 and 4. FIG. 4 shows the configuration of a conventional station.

In the figure, 25a and 25b are decoders for decoding loopback instructions received from transmission lines 3 and 4, respectively; 31a and 31b are output signals thereof; 27 is a switching control circuit that generates a control signal according to the decoding results; 32 is the switching signal which is the output thereof, 26a and 26b are the switching signals 32
The input of the transmitter 22 and the receiver 21 correspond to
This is a switching circuit that executes switching such as directly connecting the output of the transmitter and inserting a transmission/reception control circuit between the transmitter and receiver. Now, from the transmission path 3 via the receiver 21a,
Upon receiving the loopback instruction, the decoder 25a decodes it. As a result, the switching control circuit 27 controls the switching circuits 26a and 26 so that the transmission/reception control circuit 24 is inserted between the output of the receiver 21a and the input of the transmitter 22b.
b to realize a loop back from the transmission line 3 to the transmission line 4. As a result, the configuration shown in FIG. 5 is obtained. For simplicity, the decoder and switching control circuit are omitted from the figure. In the figure, the loop back indicated by the dotted line inside 26b is not necessarily required. When a conventional station receives a loopback instruction sent from a monitoring station, it simply loops back toward the monitoring station.
Since there is no relay to subsequent stations, a loopback instruction was required to specify each station individually.

In addition, if the location of the failure is unknown, it is necessary to follow the procedure of giving loopback instructions in order from the stations farthest from the monitoring station along the signal flow and tracing back until the loopback is successful, which increases the complexity of recovery control. However, the drawback was that it took a long time to recover. This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and by using the loopback instruction, there is no need to perform loopback control while selecting stations individually by knob, and it is possible to perform loopback control in a short time. The purpose is to provide a loopback method that enables recovery in time.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 6, the same reference numerals as in FIGS. 1 to 5 indicate the same or corresponding parts.

25c and 25d are decoders 31c and 31 for decoding Issai loopback instructions received from transmission lines 3 and 4, respectively;
d is the output, 28a and 28b are the transmission lines 3 and 28b, respectively.
4 abnormality monitoring circuit, 33a, 33b are its outputs, 26c
, 26d are switching circuits for directly connecting the receiver output and transmitter input or inserting a transmission/reception control circuit between the receiver output and transmitter input; 27a is a decoder; 26c receives the output of the abnormality monitoring circuit; , 26d.

Now, when the Issai loop batt instruction is received from the transmission line 3 via the receiver 21a, the decoder 25c decodes it, and thereby the switching control circuit 27a switches between the output of the receiver 21a and the input of the transmitters 22a and 22b. A switching signal 32a is applied to switching circuits 26c and 26d so that the transmission/reception control circuit 24 is inserted between the switching circuits 26c and 26d.

As a result, the configuration shown in FIG. 7 is obtained. The figure omits the switching control circuit, decoder, and abnormality detection circuit for the sake of clarity. From FIG. 7, it can be seen that the Issai loopback instruction transmitted by the transmission line 3 is looped back through the transmitter 22b of the station 2a, and at the same time
The signal is also transmitted to the subsequent station 2b by 2a, so the connection switching of 2b is also performed in the same way as 2a. As a result of the loopback of the station 2b, the receiver 21b of the station 2a can receive normal signals.
The abnormality monitoring circuit 28b in FIG. 6 detects that the reception on the transmission line 4 has returned to normal, and outputs a recovery detection signal 33b to the switching control circuit 27a. By this, 27a
cancels the loop back in switching circuits 26c and 26d. As a result, the station 2a shown in FIG. 7 returns to the configuration shown in FIG. 2. On the other hand, in FIG. 7, since the station 2b is adjacent to the failure point, the reception on the transmission path 4 does not return to normal, and a loopback state is maintained.

As described above, according to the present invention, even during loopback, the signal is relayed to the subsequent station, and the loopback is canceled when the signal looped back from the subsequent station is successfully received. Since it is attached to the station, it is possible to issue a loopback instruction, which greatly reduces switching time and simplifies switching control at the monitoring station.

[Brief explanation of drawings]

Figure 1 is a general configuration diagram of a dual loop transmission system.
Figure 2 is an internal configuration diagram of the station in a normal state, Figure 3 is a configuration diagram showing the concept of loopback, Figure 4 is a configuration diagram of a conventional station, and Figure 5 is an internal configuration diagram of a conventional station during loopback. , FIG. 6 is a block diagram of a station according to an embodiment of the present invention, and FIG. 7 is a diagram showing a part of the system configuration according to an embodiment of the present invention and the internal structure at the time of loopback in the station.

Claims (1)

[Claims] 1. A system comprising two loop transmission lines capable of transmitting signals in opposite directions and a monitoring station that monitors a plurality of stations, so that when a failure occurs in both of the transmission lines, In a leapback method of a dual loop transmission system, two stations adjacent to a faulty section each return their signals to a monitoring station, thereby isolating the faulty section and continuing operation. A loopback system characterized in that each station that receives the Issai loopback instruction from the monitoring station relays the line signal on the side that received the Issai loopback instruction to a second transmission line. 2.Equipped with two loop transmission lines that can transmit signals in opposite directions and a monitoring station that monitors multiple stations, and if a failure occurs in both of the above transmission lines, the loop transmission line adjacent to the failed section In the loopback method of a dual-loop transmission system, two stations each return signals to a monitoring station, thereby isolating a faulty section and continuing operation. Each station that receives the back instruction relays the line signal on the side that received the loopback instruction to the second transmission line, and after this relay operation, each station transfers the signal on the receiving line that has not been relayed. If it is detected that the signal on the receiving line has returned to normal, the relay operation is canceled, and if the signal on the receiving line is abnormal, the relay operation is continued.